When i had these headers installed about a year ago there was a slight leak but it never really bothered me. Now i've got a pair of cams and custom tune and she don't run so good. I had the slip-fit section's welded up which helped a lot but since u can't weld it all the way around the tubes i still have a very small leak. I think i saw someone use a T-bolt clamp but looking at them i don't see how the clamp could generate enough force to squeeze the header tube.